1. Field of the Invention
The present invention relates to a grinding machine having a device for detecting the state of wear of a grinding wheel and more particularly to a grinding machine having a device for determining whether the grinding wheel has been worn down beyond the limit of use.
2. Description of the Prior Art
Generally, in a production-type grinding machine with an automatic dressing or truing apparatus, a truing tool is slidably guided toward the axis of a grinding wheel. At the time of the truing operation, the grinding surface of the grinding wheel is trued by in-feeding the truing tool against the grinding wheel by a preselected in-feed amount. The grinding machine ordinarily incorporates a detection device which determines whether the grinding wheel has been worn down to the limit of use by detecting the advancement of the truing tool to a predetermined position by means of a dog and a limit switch actuated thereby.
Even using such a prior art detection device, unless the truing tool suffers wear, the wear status of the grinding wheel down to a limit of use can be exactly detected only by adjusting the space between the dog and the limit switch to the thickness of an abrasive layer of the grinding wheel. However, not only does the truing tool actually suffer wear, but such wear of the truing tool is also difficult to predict. Accordingly, it is impossible to set the relative position between the dog and the limit switch accurately while taking into account the prospective wear of the truing tool. Thus the prior art detection device is not able to exactly detect the wear status of the grinding tool down to the limit of use.